Electronic trigger pulse generator



Nov. 29, 1949 4 N. BISIHOP 2,489,852

ELECTRONIC TRIGGER PULSE GENERATOR Filed Dec. 4, 1944 Inventor: Nathaniel Bishop His Attorney.

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Patented Nov. 29, 1949 ELECTRONIC TRIGGER PULSE GENERATOR Nathaniel Bishop, Fairfleld, Conn., assignor to General Electric Company, a corporation of New York Application December 4, 1944, Serial No. 566,498

This invention relates to means for triggering control circuits.

Where triggering devices, such as multivibrators, for example, are employed in applications where the device must be accurately triggered, it is desirable to have the trigger pulses of short duration, steep rise to maximum amplitude and a constant frequency. Different circuits have been employed to provide steep pulses of short duration. However, the circuits heretofore used have required large units having a number of circuits in order to provide a reasonable degree of frequency stability.

It is an object of my invention to provide a new and improved circuit for providing equally spaced trigger pulses at a substantially constant frequency.

It is another object of my invention to provide a new and improved circuit which is simple in nature and employs a minimum number of circuit elements for providing equally spaced trigger pulses at a substantially constant frequency.

The features of my invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, both as to its organization and manner of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a schematic diagram of one embodiment of my invention; Fig. 2 discloses graphically some of the operating characteristics of the circuit shown in Fig. l, and Figs. 3 and 4 show different embodiments of the principles of my invention.

Referring to Fig. 1 of the drawing, there is shown an oscillatory circuit ltlof the Hartley type including a tuned circuit comprising a tapped inductance II and a capacitor l2. Either or both of the tuned circuit elements may be variable if variable frequency of oscillations is desired.

The oscillatory circuit also includes an electron discharge device of the pentode type. The cathode M is connected to a suitable tap on the coil H. The anode element i5 is connected to a suitable source of positive potential and is bypassed to ground through capacitor H. The suppressor grid i8 is shown grounded although it may be tied to the cathode if preferred. The grid element I9 is connected to one side of the tuned circuit through grid leak 20 and grid condenser 2|. The other side of the tuned circuit is grounded. It will be observed that the oscillatory circuit is the conventional Hartley circuit except that the screen grid element is not bypassed to ground.

4 Claims. (Cl. 250-36) The oscillatory circuit is biased for operation as a class C oscillator. Therefore, the electron discharge device is driven to saturation during each positive half cycle of the oscillatory wave and a substantially square pulse results on the screen grid and anode.

The substantially square waves are impressed upon a suitable frequency selective circuit, including a differentiation device, of such character as to discriminate against low frequency components such as the fundamental and lower order harmonics present in the voltage applied thereto. In Fig. 1, there is shown one form of a suitable frequency selective circuit. The screen grid control electrode or element 22 of the electron discharge device is connected to the upper end of a. screen load impedance illustrated in the form of a resistance 23. The other end of the resistor 23 is connected to the source of positive voltage. The upper end of the resistor 23 is also connected to an R. C. differentiating circuit comprising a capacitor 24 and a resistor 25.

Referring to Fig. 2, there is shown at A the sine wave of voltage appearing on the grid element l9. At B in Fig. 2 there are illustrated the substantially square voltage waves appearing on screen element 22. The square waves have the same fundamental frequency as the sine wave voltage shown at A in Fig. 2. Typical negative and positive voltage pulses appearing at resistor 25 and applied to the utilization device or circuit 33, such as a pulser, are shown at C in Fig. 2.

It will be noted that in the circuit shown there is substantially no load on the oscillator so that the circuit is very stable and the pulses ob-' tained therefrom are equally spaced apart, i. e., occur at a constant repetition rate. Either positive or negative pulses may be used for trigger ing depending upon the design of the triggering device. The oscillatory and differentiating Giff cuits may be arranged to produce only positive or only negative pulses if desired.

I Fig. 3 illustrates a second embodiment of my invention in which the substantially square pulses are taken from the anode element l5 of the electron discharge device, thereby providing pulses of a greater voltage swing. In this embodiment of my invention the screen grid element 22 is connected to a suitable source of positive poten tial through a suitable voltage dropping resistance 26 and is bypassed to ground through a capacitor 21. The anode element is connected to the source of positive potential through a suitable load impedance such as a resistor 23a. The source of positive potential is by-passed to ground through a suitable capacitor 28. The substantially square pulses from anode l are impressed on the frequency selective circuit including resistor 23a in a manner similar to that shown in Fig. 1.

In Fig. 4 there is shown an adaptation of my invention to a crystal oscillator circuit. The grid circuit includes a suitable crystal 29 shunted by resistor3fl. @The plate circuit includes suitable inductance 3| and capacitor 32. The substantially square waves appearing across a suit: able load impedance such as resistor 23b are impressed upon the differentiation circuitcomprising capacitor 24 and resistance 25.

As indicated above, any network ordevice of suitable characteristics may beemployed to differentiate pulses or voltage impressed thereon.

For example, a small inductance shunted'nbysa' damping resistor or a transformer havinglow primary impedance could be used. The important thing is to arrange the frequency selective circuit to convert thesubstantially square pulses :nnxscreengridelectrode 22 or anode i 5 to sharply apeaked :short duration pulses. Because of the :stabievnatureof theslightly loaded oscillator, these zpizlses willrbe' equally spaced apart.

While I have shown and 'desc'ribed a particular embodiment of 'imy'invention, it will be obvious tothoseskilledointtheaartthat changes and modifications: mayzbe made without departing'from anyinvention in. itszbroaderaspects, and I, therefore, aimin theyappiended: claims to cover all such .changes and :modifications as fall within the true: spirit and-:scope: ofsmy invention.

vwhatflccladmrasineweand desire to secureby LettersPa-tentof the IIIIitGdrStEt-iJES is:

i l. The :rcombination of ran oscillatory circuit comprising-ram electron zdischarge device including-ran anode electro'daza .control electrode, a cathode electrode; and.:;a screen grid: electrode, a.- source of. aanodet; operating potential connected in :circuitbetween; :said-anode'and cathode electrodes, means for impressing asubstantially sinewave: oscillatory voltage-ron:said'-control electrode, said means: comprising a--. circuit" resonant at ;a predetermined frequency: and having a terminal thereof connected :to said control electrode, .meansto bias said control electrode negatively to such .an extent that "discharge; current flows between said-cathode electrode and one :of said remaining electrodes in 1311881185 of: pulses recurring at said frequencyrandmeans forldiiierentiating the rresulting voltage variations appearing on one of the remaining-saideelectrodesrof said electrondischarge device. thereby :tonproduce a series of. sharply-peaked pulses recurring-accuratelyi at. said frequency.

.12.. The combination-of..an oscillatory .circuit including an electron -..discharge. devicerhavingaa plurality of. elements .including an anode,- a oath-- ode, a control electrode, =andta.screen grid electrade. asource. of: anodeoperatingpotential connected in circuit between sSaid: anode-and said cathode, means I for impressing a substantially sine-wave oscillatory voltageon .said control electrode,.. said. means comprising. a circuit. resonant at. a predetermined .frequency. .and having a .terminal thereof. connectedto said control electrode, means .to bias said .controlelectrode negatively to..such.. an..extent..thatv discharge. current' flows between said, cathodeeand -said screen grid ..elec trode in a series or. pulses recurring at saidfreguency, .an'd means for .difierentiating the v.re-

sulting voltage variations appearing on said screen grid electrode.

3. The combination of an oscillatory circuit comprising an electron discharge device including an anode electrode, a control electrode, a cathode electrode and a screen grid electrode, a source of anode operating potential connected in circuit between said anode and cathode elecitrodes, means for impressing 12. substantially sine-wave oscillatory voltage on said control electrode, said means comprising a circuit resonant at'a predetermined frequency and having a terrminalthereofzconnected to said control electrode, means to bias said control electrode negatively *to subhzanextent that discharge current flows "betweemsaid. cathode electrode and one of said remaining electrodes in a series of pulses recurring-cat:saiditrequency, a utilization circuit, and frequency selective means connected between onepr'the other of said electrodes and said utilization circuit, said frequency selective means being arranged -to convert the substantially square waves appearing on said oneelectrode into sharply-peaked relativeiy short=duration substaritial-lyeequally-spaced-apart pulses.

4PBhe "combination of an oscillatory circuit comprising an: electron discharge device including ananodeelectrodepa cathode, acontrol electrode, and: a 'screensgrid electrode, :a source :of anoderoperating potential connected in circuit :betweenisaid anode electrodev and said cathode, means; for impressingza substantially. sine-wave oscillatory voltage :on said control electrode, said means comprising a circuit resonantataprede" termine'd'frequency: and having aiterminal therepfcconnected. ato; said-:contr'ol:electrode, means to bias saidrcuntrol electrodemegatively to suchan extent that discharge current flows between said cathode-rand said screen grid electrode :in a. series of pulses recurring .atsaid frequency, a utilization circ.uit,..and frequency selective rneansconne'ctedr/between said;- screen agrid electrode :and saidutilization circuit,.:said frequency selective means beingarrangedrto discriminateagainst the low rtrequency componentszofthe voltage appearingsons-saidscreen gridzelectrode whereby the substantially square pulses impressed on said frequency Tselec-tive -means -.are converted into sharply-peaked relative-shortedura-tion, substantially-equally-spaced-apart pulses at the input to saidmtilizationdevice.

NATHANIEL BISHOP.

.7 REFERENCES CITED "The -foll0wingreferencesare of record in the file of this patent:

.UNITED STATES PATENTS OTHER REFERENCES The Oscillator at .Work, .John Rider (1941), John F.. .Rider Publisher, Inc, 404 Fourth Avenue, New .York, NewYork. 

